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A 24 y/o male patient is brought to your ED intubated after being found down (GCS 3) at a local event where heavy drug use is routine. It was a difficult pre-hospital intubation, RSI was not utilized and large volume aspiration occurred. Oxygen saturations during the 20-minute transport to your facility remained 70’s, and are persistently 70’s when attached to your monitor in the ED. What is your next maneuver for stabilization of this critical patient? The stabilization of patients with severe hypoxia post intubation can be intimidating for any ED provider regardless of experience level. Normally we expect hypoxia to resolve once an airway is secured, and persistent hypoxia can be anxiety provoking for all involved. It is important to have a series of maneuvers in your back pocket for these rare situations to avoid prolonged cerebral hypoxia. The “DOPES” pneumonic can help you troubleshoot potential causes of persistent hypoxia post intubation. Listed below are the elements of this approach. D= Tube DisplacementColorimetry alone can be unreliable in low perfusion states such as cardiac arrest and you may not get a convincing color change. Attach the patient to waveform capnography. (ETCO2) is the gold standard for verifying endotrachial intubation and is 100% specific. Changes or discontinuation in waveform readings can indicate tube dislodgement. If you do not have a waveform you do not have an endotracheal tube! Once you have waveform-which verifies ETT placement, verify proper ETT depth by auscultation/CXR.

O=ObstructionPay attention to ventilator alarms, high peak pressures can alert you to possible tube obstruction. Verify the patient is not biting the tube-if so place a bite block or provide more sedation, verify suction catheter or bougie can be easily passed to rule out kinked tube or large mucus plug. CXR can also indicate massive atelectasis from a mucus plug. Look for mediastinal shift TOWARDS the collapsed side as an indication of this issue. Occasionally re-intubation is required, or emergent bronchoscopy.

P=PneumothoraxPatients on positive pressure ventilation are at higher risk for spontaneous PTX, specifically COPD/asthma/trauma. Persistently hypoxic patients are also at risk for iatrogenic injury by overly anxious respiratory therapists or providers bag-valve-masking aggressively. Be suspicious of PTX in any patient that was initially hypoxic and required high PEEP to stabilize

E=EquipmentVerify all connections are intact, if so, disconnect and perform BVM with supplemental O2 and PEEP valve to rule out ventilator as potential cause of any problem, check ETT cuff pressure

S=Breath stacking/synchronyBreath stacking = increasing pressure due to inability to exhale in asthma/COPD. To combat this decrease your tidal volume and increase the time allowed to exhale. Lower respiratory rates and permissive hypercapnia may be required. Consider heavy sedation or paralysis if auto-peep persists despite ventilator adjustments.

Synchrony = Ventilator dysynchrony or “bucking” the vent in an already hypoxic patient can lead to further derecruitment. Heavy sedation, pain control, or paralysis may be required.

Ok so now you’ve checked all of these things, and the patient is persistenly hypoxic. Here are a few rescue maneuvers you may attempt to troubleshoot your patient’s care-in order:

1. PUT THEM TO SLEEP: If your patient’s respiratory rate does not match the ventilator rate make it happen! You should take complete control of the patient’s ventilation. Air hunger will increase your patient’s respiratory drive and complicate management. Adding a narcotic infusion such as fentanyl will also blunt the patient’s discomfort caused by hypercapnia

2. PARALYSIS: When putting your patient to sleep isn’t enough consider paralysis. A vecuronium bolus (10mg IV) can buy you about 45 minutes to attempt stabilizing maneuvers. Occasionally an infusion is necessary-in which case cisatracurium may be required. This requires hourly monitoring of sedation however, and generates a lot of documentation and paperwork

3. RECRUITMENT MANEUVERS: If you have reached this point and still have hypoxia it is likely you have pathology resembling ARDS. Positive pressure is the key to increasing your perfusion area. Bag-valve-mask ventilation with a PEEP valve set higher than your current ventilator PEEP may be enough to recruit atelectatic lung segments. A more aggressive recruitment maneuver is to provide 30-40 PEEP for 30-40 seconds. This is not a good option in Asthma/COPD as auto-peeping these high pressures could lead to iatrogenic pneumothorax. If your patient responds to increases in PEEP they may require a stepwise increase in PEEP on the ventilator. Increases in PEEP take time to have full effect, but decreases in PEEP will lead to immediate de-recruitment. Be sure to check plateau pressure after changes in PEEP and ensure it is lower than 30 (recommended by ARDSnet) to avoid barotrauma.

4. ADVANCED THERAPY: If all of these maneuvers have not worked you will likely require expert consultation, if you haven’t gotten it already. APRV (BiLevel) is a ventilator mode which may help with recruitment, and HFOV (oscillator) can also be useful. These both require special ventilators and in depth understanding of ventilator mechanics. Inhaled nitric oxide or prostaglandins are also useful at selectively increasing alveolar perfusion but are costly and require extra equipment.

How to correct a respiratory acidosis:

In order to correct a respiratory acidosis in a ventilated patient with this equation you must be in control of their minute ventilation, or at least have a patient with a predictable and consistent minute ventilation.

It is important to have a series of maneuvers in your back pocket for these rare situations to avoid prolonged cerebral hypoxia.

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